feat(API-1791): Add App java snippets

Author: LevFlavien

content/apps/create-app.md

@@ -29,6 +29,7 @@ immediately in this Activation URL.
 !!!include(content/apps/create-app/activate-php.md)!!!
 !!!include(content/apps/create-app/activate-nodejs.md)!!!
 !!!include(content/apps/create-app/activate-python.md)!!!
+!!!include(content/apps/create-app/activate-java.md)!!!
 
 ## Callback URL
 
@@ -38,6 +39,7 @@ Then, your application must expose a callback URL.
 !!!include(content/apps/create-app/callback-php.md)!!!
 !!!include(content/apps/create-app/callback-nodejs.md)!!!
 !!!include(content/apps/create-app/callback-python.md)!!!
+!!!include(content/apps/create-app/callback-java.md)!!!
 
 
 

content/apps/create-app/activate-java.md

@@ -0,0 +1,42 @@
+```java [activate:Java Spring]
+import java.security.SecureRandom;
+
+import javax.servlet.http.HttpServletRequest;
+import javax.servlet.http.HttpServletResponse;
+import javax.servlet.http.HttpSession;
+
+import org.apache.tomcat.util.buf.HexUtils;
+
+import org.springframework.web.bind.annotation.GetMapping;
+import org.springframework.web.bind.annotation.RestController;
+
+public class App {
+    static final String OAUTH_CLIENT_ID = "CLIENT_ID";
+    static final String OAUTH_SCOPES = "read_products write_products";
+    
+    @GetMapping("/activate")
+    public void activate(HttpServletRequest request, HttpSession session, HttpServletResponse response) throws Exception {
+        // Create a random state for preventing cross-site request forgery
+        byte[] randomBytes = new byte[10];
+        new SecureRandom().nextBytes(randomBytes);
+        String state = HexUtils.toHexString(randomBytes);
+    
+        Object pimUrl = request.getParameter("pim_url");
+        if (pimUrl == null) {
+            throw new Exception("Missing PIM URL in the query");
+        }
+    
+        // Store in the user session the state and the PIM URL
+        session.setAttribute("oauth2_state", state);
+        session.setAttribute("pim_url", pimUrl.toString());
+    
+        // Build url for the Authorization Request
+        // https://datatracker.ietf.org/doc/html/rfc6749#section-4.1.1
+        String authorizeUrl = pimUrl + "/connect/apps/v1/authorize" + "?response_type=code" + "&client_id=" + OAUTH_CLIENT_ID
+                + "&scope=" + OAUTH_SCOPES + "&state=" + state;
+    
+        // Redirect the user to the Authorization URL
+        response.sendRedirect(authorizeUrl);
+    }
+}
+```

content/apps/create-app/callback-java.md

@@ -0,0 +1,75 @@
+```java [callback:Java Spring]
+import java.net.URI;
+import java.net.http.HttpClient;
+import java.net.http.HttpRequest;
+import java.net.http.HttpRequest.BodyPublishers;
+import java.net.http.HttpResponse;
+import java.net.http.HttpResponse.BodyHandlers;
+import java.nio.charset.StandardCharsets;
+import java.security.MessageDigest;
+import java.security.SecureRandom;
+
+import javax.json.Json;
+import javax.json.JsonObject;
+import javax.servlet.http.HttpServletRequest;
+import javax.servlet.http.HttpSession;
+
+import org.apache.tomcat.util.buf.HexUtils;
+import org.springframework.web.bind.annotation.GetMapping;
+
+public class App {
+    static final String OAUTH_CLIENT_SECRET = "CLIENT_SECRET";
+    
+    @GetMapping("/callback")
+    public String callback(HttpServletRequest request, HttpSession session) throws Exception {
+        Object sessionState = session.getAttribute("oauth2_state");
+        String stateParam = request.getParameter("state");
+    
+        // We check if the received state is the same as in the session, for security.
+        if (sessionState == null || !sessionState.equals(stateParam)) {
+            throw new Exception("Invalid state");
+        }
+    
+        Object code = request.getParameter("code");
+        if (code == null) {
+            throw new Exception("Missing authorization code");
+        }
+    
+        Object pimUrl = session.getAttribute("pim_url");
+        if (pimUrl == null) {
+            throw new Exception("No PIM url in session");
+        }
+    
+        // Generate code challenge
+        byte[] randomBytes = new byte[30];
+        new SecureRandom().nextBytes(randomBytes);
+        String codeIdentifier = HexUtils.toHexString(randomBytes);
+    
+        MessageDigest digest = MessageDigest.getInstance("SHA-256");
+        byte[] codeChallengeBytes = digest.digest((codeIdentifier + OAUTH_CLIENT_SECRET).getBytes(StandardCharsets.UTF_8));
+        String codeChallenge = HexUtils.toHexString(codeChallengeBytes);
+    
+        String accessTokenUrl = pimUrl + "/connect/apps/v1/oauth2/token";
+    
+        JsonObject json = Json.createObjectBuilder()
+                .add("client_id", OAUTH_CLIENT_ID)
+                .add("code_identifier", codeIdentifier)
+                .add("code_challenge", codeChallenge)
+                .add("code", code.toString())
+                .add("grant_type", "authorization_code")
+                .build();
+    
+        // Do a POST request on the token endpoint
+        HttpClient client = HttpClient.newHttpClient();
+        HttpRequest authorizeRequest = HttpRequest.newBuilder()
+                .uri(URI.create(accessTokenUrl))
+                .header("Content-Type", "application/json")
+                .POST(BodyPublishers.ofString(json.toString()))
+                .build();
+    
+        HttpResponse<String> response = client.send(authorizeRequest, BodyHandlers.ofString());
+    
+        return response.body();
+    }
+}
+```